### Coordinated Universal Time(UTC):
It is the primary time standard by which the world regulates clocks and time. To get current UTC time in Python, we can use `datetime` module.
```py
In [5]: import datetime
In [6]: datetime.datetime.now(datetime.timezone.utc)
Out[6]: datetime.datetime(2014, 11, 22, 14, 42, 21, 34435, tzinfo=datetime.timezone.utc)
```
### Unix time / POSIX time / Epoch time:
It is a system for describing instants in time, defined as the number of seconds that have elapsed since 00:00:00 Coordinated Universal Time (UTC), Thursday, 1 January 1970, not counting leap seconds. To get Unix timestamp, we can use `time` module.
```py
In [8]: import time
In [9]: time.time()
Out[9]: 1416667432.5664258
In [10]: int(time.time())
Out[10]: 1416667766
```
With Pyhon 3.4, we can directly get timestamp from UTC.
```
In [13]: datetime.datetime.utcnow().timestamp()
Out[13]: 1416649608.58369
```
### Conversions:
To convert Unix timestamp to UTC we can use `utcfromtimestamp` function.
```py
In [21]: datetime.datetime.utcfromtimestamp(1416668401)
Out[21]: datetime.datetime(2014, 11, 22, 15, 0, 1)
```
To convert UTC time object to Unix time, we can use `strftime` function.
```py
In [38]: dt = datetime.datetime.now()
In [39]: dt.strftime("%s")
Out[39]: '1416668938'
```
Alternatively, we can use `calendar.timegen` function.
```py
In [46]: import calendar
In [47]: dt = datetime.datetime.utcnow()
In [48]: calendar.timegm(dt.utctimetuple())
Out[48]: 1416669150
```